Picketers have blocked roads causing massive traffic disruption while more than 100 police have been injured by petrol bombs and other missiles since the December 3 vote by Belfast City Council.

Speaking after the meeting at Stormont House, Mrs Villiers said: "The message that we would both like to take out here to the wider community and to the wider world is one that the violence is intolerable and these protests have to come off the streets. They have to be replaced by dialogue.

"But I think we should also keep this in proportion and reassure the rest of the world that Northern Ireland is still a great place to do business in and still a great place to visit.

"I am confident that the political parties will find a way forward in Northern Ireland to addressing the kind of concerns that have been addressed in recent weeks."

She played down the fact that the First and Deputy First Ministers had not yet appeared together in public to speak about the flag issue.

"The First and Deputy First Minister are working incredibly hard on these matters," she said. "They are working together on these matters. It is a tradition after these quad meetings for the Secretary of State and the Tanaiste to conduct the press conference."

Meanwhile, Mr Gilmore described today's meeting as positive and productive.

He said: "We reaffirmed, the four of us, the condemnation of the street violence and our support for the PSNI in the challenging work that they have to do.

"Clearly some of the images which are coming out of Northern Ireland over the past number of weeks are worrying because of their potential to undo so much positive that has happened over the past number of years."